Original URL: http://www.theregister.co.uk/2008/10/22/chrome_carpet_bombing/

Chrome sweeps carpet-bombing bug under the rug

Second fix only for developers and still threadbare

By John Leyden

Posted in Security, 22nd October 2008 11:14 GMT

Google has issued a second partial fix to Chrome for an infamous carpet-bombing vulnerability that affected multiple browser packages, but it is only available via the developer version of its browser.

The patch has not been published as an automatic update to general users, though it is possible for the tech-savvy to get the security fix by changing default settings on the browser. Other lesser security updates are also developer-only.

The carpet-bombing bug is a blended threat that kicks in when Apple's Safari browser is installed on the same systems as other browser packages. The flaw means that (potentially) executable files might be automatically downloaded onto a user's desktop where they might be subsequently executed. The vulnerability was identified by independent security researcher Billy Rios in May and patched by Apple - after initial denials that the bug was a problem - in June.

That still left other browser makers with the job of releasing updates to thwart attacks on systems running insecure Safari software. IE and Firefox updates were available in July.

Google Chrome only emerged blinking into the world at the start of September. It too was vulnerable to the carpet-bombing bug. Google published a workaround in early September (less than a week after Chrome became available) that meant the desktop is not the default directory for downloads. Tacitly conceding that this partial workaround is not enough, Google has now made the download behaviour of developer versions of Chrome more secure.

Potentially executable files (eg exe, dll, bat, etc.) are now downloaded to unconfirmed_*.download files.

"In the browser, you're asked if you want to accept the download. Only after you click Save is the unconfirmed_*.download file converted to the real file name. Unconfirmed downloads are deleted when Google Chrome exits," writes Mark Larson, a Google Chrome program manager, on the Google Chrome blog .

The changes in Dev Release: 0.3.154.3 of Chrome are themselves potentially incomplete, because if Google crashes then these unconfirmed files may not be deleted, security researcher Aviv Raff told Computerworld. Version 0.3.154.3 also fixes crash and plug-in performance glitches.

The hoi polloi outside the developer community can choose to receive all published security updates, including those normally available only to developers, via the Channel Chooser plug-in (as explained here). Chrome - which is still in beta - accounts for an estimated one per cent of the browser market. ®